This invention relates to cellular communications systems and particularly to the transmission and reception of data within a cellular network.
Cellular radio telecommunications networks generally include mobile services switching centres (MSC) coupled to a public switched telephone network (PSTN), base transceiver stations (BTS) and radio telephone subscriber units often referred to as mobile stations.
Each of a plurality of base transceiver stations generally defines a geographic region or cell proximate to the BTS to produce coverage areas. Cell sizes range typically from 200 meters in diameter in urban areas to 60 kilometers in rural areas. Often, base transceiver stations are positioned at regular intervals close to main roads in order to give communications service coverage to motorists. Each BTS comprises the radio frequency components and the antenna for communicating with the mobile stations. Usually, several base transceiver stations are under the control of a base station controller (BSC) which in turn communicates directly by a land line or microwave link with an MSC. Several base station controllers may report to one MSC.
Multiple access techniques permit the simultaneous transmissions from several mobile stations to a single BTS. The GSM System (global system for mobile communications) uses time division multiple access (TDMA), in which a communications channel consists of a time slot in a periodic train of time intervals over the same frequency. Each mobile station is allocated one specific time slot for communication with a BTS in a repeating time frame. Another type of multiple access technique, and one proposed for the third generation universal mobile telecommunication system (UMTS) is known as code division multiple access (CDMA) which employs spread-spectrum signaling. Individual users in the CDMA communications network use the same RF carrier frequency, but are separated by the use of individual spreading codes. Hence, multiple communications channels are allocated using a plurality of spreading codes within the portion of radio spectrum, each code being uniquely assigned to a mobile station.
By means of the aforementioned network components, a cellular network is able to (amongst other things) monitor the number of calls made by a mobile station, control the xe2x80x9chandoverxe2x80x9d of the communications link from the mobile station to the base transceiver stations as it moves from one cell to another, calculate the round trip time (often referred to as the timing advance) of the communications link between the mobile station and the BTS and track a mobile station""s location within the network by means of a location update sequence.
In addition to speech, there is a trend for other forms of data (e.g. fax, E-Mail, video and multi-media) being delivered through radio telecommunications networks. Since several cellular networks supporting different data rates (e.g. GSM General Packet Radio System (GPRS), the modified form of GSM known as EDGE and UMTS) are to be available in the same geographical area, it is desirable to optimise the delivery of these data in terms of resources allocated by the network (e.g. data rates) and the needs and/or behaviour of the subscriber. This optimisation is of particular interest in the context of UMTS deployment in Europe, which will exist it its first stage in isolated spots (e.g. major cities). As an example, consider a subscriber in a car, intending to send a file of several M-bytes (a typical size of today""s documents in use) over the GSM network. Due to very low available bit rates (9.6 kbits today, more if the cell supports general packet radio services), the use of the GSM network presents several drawbacks. For example, the GSM link needs to be maintained for a comparatively long time. This can necessitate multiple handovers whilst the subscriber is in motion and the subsequent increased probability of a call being dropped. Furthermore, the probability of having a transfer problem is proportional to the connection time (it is well know that on the Internet, downloading a file of several M-bytes is a hazardous operation using a low bit rate modem).
For the above reasons, it is beneficial to plan for the data transmission before it is executed. For example, if the future bandwidth availability can be estimated, then the data transmission process can be optimised.
U.S. Pat. No. 5,572,221 (Marveli et al) discloses methods for predicting movements of mobile radio transceivers, thus facilitating selection of a cell for future handover. This method""s criteria are static and do not offer dynamic selection to always best quality service. Besides, this method relies on learning the movement patterns of each of the mobile radio transceivers. As these are linked to the personal habits of users, the learning task is burdensome and leads to unreliable results.
This invention aims to provide a method and apparatus for predicting the future trajectory and hence communication capabilities of a mobile station, thereby permitting the network to plan and execute optimally data delivery to or from the mobile station.
According to a first aspect of the invention, apparatus for controlling the transmission of data between a base station and a mobile station in a cellular radio telecommunications network comprises;
Means for monitoring and storing data relating to the movements of a plurality of individual mobile stations in a designated geographical area within the network,
Means for grouping those mobile stations comprising the plurality of individual mobile stations which share common movement characteristics and for storing said common movement characteristics for each group,
Means for receiving a request for transmission of data to or from a mobile station,
Means for matching past monitored movements of the mobile station with the stored characteristics of one of said groups,
Means for predicting a trajectory of the mobile station from the stored characteristics of said one of said groups,
And means for controlling the transmission of data between the base station and the mobile station dependent upon the predicted trajectory.
The apparatus may be incorporated in a mobile switching centre or in a base station controller, for example.
According to a second aspect of the invention, a method for controlling the transmission of data between a base station and a mobile station in a cellular radio telecommunications network includes the steps of;
Monitoring data relating to the movements of a plurality of individual mobile stations in a designated geographical area comprising the network,
Storing said data,
Grouping those mobile stations comprising the plurality of mobile stations which share common movement characteristics,
Storing said common movement characteristics for each group,
Receiving a request for transmission of data to or from a mobile station,
Matching past monitored movements of the mobile station with the stored characteristics of one of said groups,
Predicting a trajectory of the mobile station from stored characteristics of said one of said groups,
And controlling the transmission of data between the base station and the mobile station dependent upon the predicted trajectory.
Hence, the invention is able to predict the trajectory of a mobile station by previously observing the behaviour of a whole population of the mobile stations over a geographical area, which preferably comprises many cells.
Monitoring of the movements of the mobile station may be done by utilising any one of several measurement techniques known in GSM systems. For example, the mobile station can be tracked (by the MSC, for example) as it hands over from one BTS in a first cell to a second BTS in a second adjacent cell whilst a call is in progress. If a call is not in progress and the mobile station is in idle mode, then the mobile station can be tracked by monitoring its location update requests as it moves from one group of cells having a first local area identity to another group having a second local area identity. The above and other tracking methods are described in the Applicants co-pending Application GB 9818294.2.
The means for controlling the transmission of data maybe configured to adjust data rates or to delay commencement of transmission for a certain period of time, for example.
By being able to predict where the mobile station will be when it receives or transmits its data, the reception/transmission process can be optimised. For example, if is predicted that the mobile station will soon move outside the network""s limits, then a fast data rate can be allocated to the transmission.
Preferably, stationary mobile stations in the monitored population are ignored by the grouping process. Such mobile stations do not make a useful contribution to the overall learning process exhibited by the invention. If one particular mobile station is stationary for a long period of time, the best decision is for the data requested to be transmitted immediately at some fixed data rate.
It is not possible to make a completely correct prediction for all mobile stations. However, if a wrong decision is taken, nothing critical will happen (i.e. the call drop rate and quality of service will be the same as it would have been without the learning process offered by the invention). However, the predictions derived from the statistical observation of a population of mobile stations, will statistically improve the probability of making the right decision, thus improving the overall quality of service and call drop rate.